title: Dexamethasone accelerates degradation of aryl hydrocarbon receptor (AHR) and suppresses CYP1A1 induction in placental JEG-3 cell line.
abstract: The JEG-3 choriocarcinoma cell line has been proposed as a model cell line of human placental trophoblast for induction studies via aryl hydrocarbon receptor (AHR). We examined whether glucocorticoid dexamethasone influences AHR-mediated induction of CYP1A1 enzyme in the JEG-3 cell line. We found that dexamethasone dose- and time-dependently suppresses CYP1A1 transactivation in gene reporter assays, CYP1A1 mRNA induction, and upregulation of 7-ethoxyresorufin-O-deethylase (EROD) activity by 3-methylcholanthrene (MC) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in JEG-3 cells. Co-transfection of JEG-3 cells with glucocorticoid receptor (GR) expression construct and treatment with dexamethasone abolished the effect of MC on CYP1A1 promoter construct in transient transfection gene reporter assays. RU486, a GR antagonist, suppressed the effect of dexamethasone on MC-induced transactivation of AHR responsive reporter constructs. We also found that dexamethasone stimulates both ligand-dependent and ligand-independent degradation of AHR but not of aryl hydrocarbon receptor nuclear translocator (ARNT) protein in JEG-3 cells. In experiments with proteasome inhibitors MG132 and bortezomib, we found that the degradation is not sensitive to proteasome inhibition in JEG-3. We can conclude that dexamethasone suppresses AHR-mediated CYP1A1 induction in JEG-3 cells through the unique mechanism of AHR-GR crosstalk, which involves accelerated degradation of AHR.
authors.affiliation: Institute of Molecular and Translation Medicine, Faculty of Medicine and Dentistry, Palacky University in Olomouc, Hnevotiska 5, 779 00 Olomouc, Czech Republic; Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University in Prague, Heyrovskeho 1203, Hradec Kralove 500 05, Czech Republic.
authors.forename: Lucie
authors.initials: L
authors.lastname: Stejskalova
authors.forename: Alice
authors.initials: A
authors.lastname: Rulcova
authors.forename: Radim
authors.initials: R
authors.lastname: Vrzal
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Dvorak
authors.forename: Petr
authors.initials: P
authors.lastname: Pavek
mesh_terms: D051784:Aryl Hydrocarbon Receptor Nuclear Translocator / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D019363:Cytochrome P-450 CYP1A1 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D017930:Genes, Reporter; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D008748:Methylcholanthrene / Q000633:toxicity; D010920:Placenta / Q000187:drug effects / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020239:Receptor Cross-Talk; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism*; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation; D015854:Up-Regulation
chemical_list: D005938:Glucocorticoids; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D011965:Receptors, Glucocorticoid; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D008748:Methylcholanthrene; D003907:Dexamethasone; C569463:CYP1A1 protein, human; D019363:Cytochrome P-450 CYP1A1
keywords: Aryl hydrocarbon receptor; CYP1A1; Choriocarcinoma cell line; Glucocorticoid receptor; MG132; Proteasome